At the present time, a common arrangement for a car washing installation provides a vehicle path, along which the cars travel. Often, a mechanism is provided to control and guide the movement of the cars along the path. To wash the cars, various equipment is provided along the path. Such equipment applies water to the vehicle body and washing compounds as required. Often, various rotatably mounted brushes are provided to wash and polish the surface of the vehicle. To accommodate different vehicle sizes etc., these brushes are usually rotatably mounted on the end of an arm. Some automatic guidance arrangement is then provided, to move the arm transversely across the path on the end of the arm, so that it is always at a correct position relative to a vehicle body.
Thus, our earlier Canadian Pat. No. 1,183,758 discloses an automobile washing apparatus, which includes a pivoting arm assembly. The arm assembly has primary and secondary arms, and a brush rotatably mounted about a vertical axis at one end. The mechanism is such that the brush will travel across the front of a vehicle, along one side and then across the back of the vehicle, returning to a rest position.
Whilst mechanisms such as that outlined above can provide thorough washing over the majority of a vehicle body, the current shape of car bodies presents some difficulties. In particular, the wheel wells in the body sides and the wheels themselves are difficult to clean. The apparatus of our earlier Canadian patent has brushes which extend the full height of the car. Consequently, although they can accurately follow the side of the car, they will not enter the wheel wells significantly, which can result in them being improperly cleaned. This problem is common to washing apparatus, having brushes extending the height of the vehicle.
Accordingly, proposals have been made for the provision of special side brushing or washing wheels, specifically arranged for scrubbing, washing etc. the rocker panels and wheels of a vehicle. One such proposal can be found in the Belanger U.S. Pat. No. 4,530,126. This apparatus includes on each side, so-called side wheel assemblies, for automatically scrubbing, washing and polishing the sides, rocker panels and wheels of a vehicle. Each assembly includes a pair of parallel and spaced apart wheel arms, each being pivotally mounted at one end. A scrubbing, washing and polishing wheel of cloth material is pivotally mounted at the other end of each arm. The arms are connected, so as to form a pivoted parallelogram linkage. The wheels of the two arms are rotated in opposite directions. This has the advantage of providing thorough cleaning of the relevant parts of the car; particularly when cleaning irregular surfaces such as wheels and the periphery of wheel wells etc., a single rotating brush may not provide thorough cleaning.
A disadvantage with this arrangement is that whilst the angle of one arm and the direction of rotation of its wheel naturally tends to urge the wheel away from the vehicle, because the other wheel rotates in the opposite direction the reverse is true. Thus, for the other wheel, its direction of rotation can pull it towards the vehicle. This is a particular problem with wheel wells. When the two brushes on their parallelogram linkage encounter a wheel well, one brush can catch the edge of the wheel well and pull itself into the wheel well. As it further enters the wheel well, it becomes more strongly engaged with the side of the body, which tends to increase the force urging it into the wheel well. In extreme cases, the wheels can damage the vehicle body, e.g. by bending edges of plates around the wheel well.
This problem has been recognized and is addressed in the Belanger U.S. patent by providing a pneumatic-hydraulic control circuit. This relies upon a pilot operated check valve, that is controlled by pneumatic pressure. A three-way valve in a pneumatic supply line controls the check valve. In effect, the check valve is controlled so that, in the absence of a vehicle body, it is open, to permit the side scrubbing wheels to extend out, ready for the next vehicle body. When a vehicle is present, the pilot check valve is closed. This in effect prevents extension of the side scrubbing wheels outwards, and only permits them to move inwards. When working correctly, this will prevent the side scrubbing wheels being drawn or sucked into a wheel well. However, this arrangement has a number of disadvantages. Firstly, when the check valve is closed, the movement of the side scrubbing wheels is restricted, so that they may not accurately follow the side profile of a vehicle. More importantly, the control depends on a relatively complex control system involving both pneumatic and hydraulic components, and numerous valves, reservoirs etc. If the control system malfunctions, then it is possible for a side scrubbing wheel to be drawn into a wheel well, with possible resultant damage to the vehicle body.